As industrial applications have evolved and grown more complex, the piping products and systems that serve them have had to keep pace.
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While many pipe manufacturing methods exist, the most prominent discussion in the industry compares electric resistance welded (ERW) vs. seamless (SMLS) steel pipe.
Both ERW and seamless steel pipe manufacturing methods have been in use for decades; over time, the methods used to produce each have advanced. So which is better?
Welded pipe starts out as a long, coiled ribbon of steel called a skelp. The skelp is cut to the desired length, resulting in a flat rectangular sheet. The width of that sheet&#;s shorter ends will become the pipe&#;s outside circumference, a value that can be used to calculate its eventual outside diameter.
The rectangular sheets are fed through a rolling machine that curls the longer sides up toward one another, forming a cylinder. In the ERW process, high-frequency electrical current is passed between the edges, causing them to melt and fuse together.
An advantage of ERW pipe is that no fusion metals are used and the weld seam cannot be seen or felt. That&#;s opposed to double submerged arc welding (DSAW), which leaves behind an obvious weld bead that must then be eliminated depending on the application.
Welded pipe manufacturing techniques have improved over the years. Perhaps the most important advancement has been the switch to high-frequency electric currents for welding. Prior to the s, low-frequency current was used. Weld seams produced from low-frequency ERW were more prone to corrosion and seam failure.
Most welded pipe types require heat treatment after manufacture.
Seamless piping begins as a solid cylindrical hunk of steel called a billet. While still hot, billets are pierced through the center with a mandrel. The next step is rolling and stretching the hollow billet. The billet is precisely rolled and stretched until it meets the length, diameter and wall thickness as specified by the customer order.
Some seamless pipe types harden as they&#;re manufactured, so heat treatment after manufacturing is not required. Others do require heat treatment. Consult the specification of the seamless pipe type you&#;re considering to learn whether it will require heat treatment.
ERW and seamless steel piping exist as alternatives today largely due to historical perceptions.
Generally, welded pipe was considered inherently weaker because it included a weld seam. Seamless pipe lacked this perceived structural flaw and was considered safer. While it&#;s true that welded pipe does include a seam that makes it theoretically weaker, manufacturing techniques and quality assurance regimens each have improved to the extent that welded pipe will perform as desired when its tolerances aren&#;t exceeded. While the apparent advantage is clear, a critique of seamless piping is that the rolling and stretching process produces an inconsistent wall thickness compared to the more precise thickness of steel sheets destined for welding.
The industry standards that govern the manufacture and specification of ERW and seamless steel pipe still reflect those perceptions. For example, seamless piping is required for many high-pressure, high-temperature applications in the oil & gas, power generation and pharmaceutical industries. Welded piping (which is generally cheaper to produce and is more widely available) is specified across all industries as long as the temperature, pressure and other service variables do not exceed parameters noted in the applicable standard.
In structural applications, there&#;s no difference in performance between ERW and seamless steel pipe. While the two can be specified interchangeably, it wouldn&#;t make sense to specify for seamless when cheaper welded pipe works equally well.
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An important note to make as piping products are specified for a project is that the specification books (such as those provided by ASTM, ASME, ANSI and API, among others) that engineers use to guide the specs they write only list pipe grades without referencing whether they&#;re produced via ERW or seamless pipe manufacturing. Not all grades can be produced by both means.
For example, a potential mix-up can occur if an engineer specifies welded pipe with a large outside diameter and wall thickness without knowing it would be impossible to manufacture it. This error would likely go unnoticed until a purchase order is placed, at which time a pipe supplier would notify the customer that the order couldn&#;t be fulfilled as written.
Also, a good grasp of industry standards could lead to cost savings. The A106 and A53 carbon steel pipe standards are a good example. In this article, we discuss how pipe complying with the former must be seamless while pipe complying with the latter can either be seamless or welded. For example, if an engineer must follow the A53 standard on a given project, he or she may still have the flexibility to choose which type to specify based on the specifics of the application.
American Piping Products stays fully-stocked with the best inventory of welded and seamless steel piping products in the industry. We source our stock from mills around the world, ensuring buyers get the pipe the need faster regardless of any applicable statutory restrictions.
In our steel pipe buyer&#;s guide, we&#;ll help you navigate the piping procurement process from start to finish to ensure you get what you need as quickly as possible when it&#;s time to buy. If a piping purchase is in your near future, request a quote. We&#;ll provide one that gets you exactly the products you need&#;fast.
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Get the buyer's guideOil and Gas Industry:
The oil and gas industry relies heavily on ERW pipes for their transportation and distribution networks. ERW pipes possess excellent strength and durability, making them ideal for carrying crude oil, natural gas, and refined petroleum products over long distances. Their uniform thickness and high dimensional accuracy ensure efficient and reliable performance in demanding environments. Explore the benefits below.
- Strength and Durability: ERW pipes exhibit exceptional strength and durability, making them highly suitable for the oil and gas industry's demanding conditions. These pipes are manufactured from high-quality steel, ensuring structural integrity and the ability to withstand extreme temperatures, pressures, and environmental factors. Their robustness ensures safe and reliable transportation of crude oil, natural gas, and other hydrocarbon products over long distances.
- Cost-effectiveness: ERW pipes are known for their cost-effectiveness, making them an attractive choice for the oil and gas industry. Compared to other types of pipes, such as seamless pipes, ERW pipes offered by Tube Trading Co. - the most distinguished ERW pipe provider in Gujarat , are more affordable. Their efficient manufacturing process and readily available raw materials contribute to their competitive pricing. In the oil and gas industry, where large quantities of pipes are required for extensive pipeline networks, the cost savings offered by ERW pipes can be significant.
- Welding Efficiency: The electric resistance welding process used to manufacture ERW pipes ensures excellent welding efficiency. The longitudinal weld seam of ERW pipes is created by applying high-frequency electrical current to the edges of the steel strip. This results in a strong and reliable weld joint. The welding process is highly automated, ensuring consistent and precise welds throughout the pipe length. The efficient welding technique of ERW pipes reduces production time and enhances productivity in the oil and gas industry.
- Dimensional Accuracy: ERW pipes offer excellent dimensional accuracy, which is crucial for the oil and gas industry's infrastructure. The manufacturing process of ERW pipes allows for tight tolerances and consistent wall thickness. This dimensional consistency ensures compatibility with various fittings, valves, and connectors used in the industry. It also facilitates the efficient flow of fluids through the pipelines, minimizing pressure drops and optimizing overall system performance.
- Corrosion Resistance: The oil and gas industry operates in corrosive environments, and protecting pipelines from corrosion is of utmost importance. ERW pipes are coated with anti-corrosive materials to enhance their resistance to corrosion. These coatings, such as epoxy or polyethylene, provide a protective barrier against corrosive substances and extend the lifespan of the pipes. The corrosion resistance of ERW pipes ensures the integrity and reliability of the oil and gas transportation infrastructure.
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